Electromechanical resonator



Nov. 7, 1933. c. w. HANSELL ELECTROMECHANICAL RESONATOR Filed April 8. 1929 L L m n R 0m W m m Wm M 2 m c Patented Nov. 7, 1933 1,934,061 1 ELECTROMECHANICAL RESONATOR Clarence W. Hansell, Rocky Point, N. Y., assignor to Radio Corporation of America, a cor- 1 poration of Delaware Application April 8, 1929. Serial No. 353,285-

12 Claims.

' This invention relates to a mechanical oscillator and deals more specifically with an electromechanical oscillator having i ts frequency controlled by .the period of mechanical vibration of cuit; such as, for example, maintaining constant" any magnetic material as the vibrating element] It is a further object ofthis inventionto provide a mechanical oscillator which is highly efficient in its operation hut Which is simple and cheap to construct.

Further, it is an object of this invention to provide an electro-mechanical oscillator in which increased forces acting .upon the rod may be realized.

And finally, it is afurther object of this invention to provide an electro-mechanical oscillator which does not rely-upon either the piezo-electric effect or the principles of magnetostriction for its operation.

These and other objects of the invention will be readily apparent to those skilled in the art.

from. the following description taken in comiection with the accompanying drawing in which: Fig. 1 is a diagrammatic representation of an electro-mechanical oscillator constructed in accordance wth the principles of this invention; 1

Fig. 2. shows the device ofFig. 1 applied toa vacuum tube device; and 1 Fig. 3 shows the present invention applied to a filter circuit.

Referring in detail to Fig. 1, the electro-mechanical oscillator or resonator is seen to comprise a magnet 10- generally of U-shape, providedwith a coil 11 wound upon said magnet 10, the

terminals of the coil being connected to anysuitable direct current supply, which serves as a means to polarize the magnet 10. In the field of the magnet 10, between the north and south poles thereof, as. indicated in the'drawing, is supported avibrator rod 12 of any suitable magneticmaterial. The dimensions of the rod are chosen to give the same a predetermined natural period .of vibration. The rod or vibrator 12 is supported in any suitable manner to permit; free vibration of the same.- Wound around the vibrator 12 isa coil 13, the terminals of whichare' adapted to be connected'to the alternating current source, upon which the oscillator is to. exercise control- The coil 13 is dimensioned substam tially to enclose the Inagnetic-iield produced by '10.. The'operation of this described as follows: .a

The magnet 10 has a normally constant mag device briefly may." be

netic field due to the flow of direct, current.

through the coil 11'. Whenthe rod' l2; is placed in the field of the magnet .10 assh'own, there is a certain change in dimensionsof the rod 12, due to theaction of the magnetic field thereon. Now, when alternating current fiows'throu'gh the 001113 it produces variations in the strength 'of the field of the magnet 10, thus causing variations in thedimensions of the rod 12. The variations in the dimensions of the rod follow thevariations in the effective magnetic field acting theree on, and it. therefore follows that if such field ,is varied periodically, at a certain. frequency, the rod will'respond and vibrate at that frequency. It has been found that when the frequency of the alternating current flowing through the coil 13 is substantially in resonance with the natural period of mechanical vibration of the rod 12, the rod vibrates at a maximum amplitude and the reaction of the rod upon the alternating current circuit is very powerful. The reaction of the red at resonance is utilized to'give thefrequency control'when. the device is connected toa vacuum tube generator; and for the filter effect when the f device is used in a filter'circuit; In fact, the electro-mechanical oscillator or resonator may be used for all purposes for which the piezo-electric crystal and magnetostriction oscillator have been used. I

Referring to Fig. 2 the electr'o-mechanical resonator is shown connected to a vacuum tube circuit for the purpose of maintaining the frequency of oscillation of the tube constant. The vacuum tube 20 is provided-with the input circuit 21 and output circuit/22 in a manner well understood in the art. The coil 13 of the reso- I when the frequency of current flowing in the input circuit of the vacuum tube 20 is in resonance with the mechanical period of vibration of the vibrator rod 12, the latter will react powerfully f upon thev input circuit and maintain the frequency oscillation of the tube constant;

7 InFig. 3 there is shown an arrangementwherd by the electro-mechanical resonator of the present invention may be utilized in a filter circuit. 10 A primary circuit 30 is coupled to a secondary nator. It will be understood that when the secondary circuit 31 is traversed by a current of a frequency near resonance with the natural period of mechanical vibration of the rod 12, at which the reaction of the rod is equivalent to that of a condenser, the rod 12 will react upon the circuit 31 to balanceout its inductance and cause the flow of that particular frequency, thus acting as afilter with respectthereto. The rod 12 may be suitably dime'nsionedto' have the necessary frequency response and sharpness of cut-off.

While there have been disclosed herein certain specific embodiments of the invention, it is to be understood that the scope of the present invention is not 'limited'to the details'disclosed; but

is limited only to the pendedclaims.

extent indicated in the apclaim is:

rod of magnetic material, means to vibrate said rod in the direction of its length, said means com prising a first-magnetic device to exert a steady 55' a variable second magnetic device to react upon said first magnetic device tovary the'said magnetic pull at opposite ends of said rod where the magnetic flux leaves the'rod.

ing an input and output circuit, means connected to only'one of said circuits constructed and ar-. ranged to maintain the frequency of said generatorfsubstantiallyconstant, said means comprising'in combination, a magnet, a coil connected to said one circuit and adaptedito be traversed by an alternatingcurrent which produces a magnetic'field, and a vibratory rod mounted in relation to the fields of said magnet and said coil so that said fields'together stimulate said rod to vibrate mechanically, said rod producing through said mechanical vibrations an electrical reaction which controls thefrequency of said oscillation generator.

V 3. In a vacuum tube oscillation generator having an input and'outputcircuit, means connected to'only one of said circuits constructed and arranged to maintain the frequency of said gen crater-substantially constant, said means. comprisingin' combination, a magnet, a coil connect- I O 6 ed to said one circuit and adapted to be, traversed by an alternating current which produces a magnetic field, and a vibratory rod mounted in relation to" the fields of. said magnet and said coil so that said fields together stimulate'said rod to vi-o brate mechanically, said rod producing through saidmechanical vibrations an'electrical reaction I which controls the frequency of said oscillation.

' generator.

ll In avacuum tube oscillation generator havingan input and-output circuit, means connected to only one of said circuits constructed and arranged to maintain the frequency of said gen- 1;", erator substantially constant, said means com.

prising in combination a rod of magnetic macircuit 31 which includes the coil l3of the reso- 'magnetic field, a vibratory element located in- "Having thus described my invention'what 1'. In an electro magnetic resonator having a magnetic pull'at-oppo siteends of said rod, and' '2. Ina vacuum tube oscillation generator'have terial, means to vibrate said rod in the direction of its length, said means comprising a first magnetic device constructed and arranged to exert a strain at opposite ends of said rod, and a variable second magnetic device constructed and arrangedto react uponlsaid first magnetic de vice whereby'to vary the strain at opposite ends of said rod, and to cause the same to vibrate mechanically and to-produce through said mechanical vibrations an electrical reaction which maintains substantially constant the frequency of said generator. p

5. An electro-mechanical resonator having, in combination, a U-shaped magnet producing a termediate the ends, of said magnet, said vibratory element beingsubjected by said field to a magnetic pull" at its opposite ends, a coil surrounding said element, and means for applying an alternating current to said coil for producing variations, in the length of said element in-the direction of'said-magnetic field.- 7 r 6'. An electro-mechanical'resonator having a rod of magnetic material, mag'netmeans'at both ends of said rod for exerting by means of a magnetic field a steady electro mechanic'alforce in the direction 'of the length of said -rod,'and circuit'means for varying the magnetic field to produce variations in thelength of said rod-in the direction 'of said magnetic field by a variation in said electro-mechanical force where the magnetic 'fiux leaves said rod. v 1 V '7 'An electro-mechanical resonator having,'in combination, a magnet of substantially u shaped form, one end of said magnet being of positive polarity and the other end of ne'gative'polarity,

a longitudinally vibratory element located intermediate the ends of said'magnet and physically separatedtherefrom, said element being subjected by said field to a magnetic pull at its op'-; posite ends, a coil surrounding said element, and means for applyingan alternating current to said coil 'for producing variations in the length of said magnetic field;

8. In combination, a rod of magnetic non-mag- 12E) netostrictive material, said rod having free ends and being so dimensioned as ,to have a natural period ofmechanical vibration, corresponding to' a desired-frequency of operation, in the direction of its longitudinal ,axis,:means causing a steady, 15 magnetic field to fiow.:.through one end of said rod and out of the other end of said rod where-' by saidrod is subjected to'la mechanical stress applied substantially at the ends-thereof where said field'fiows into and out of. saidrod, said 1 2;; stress acting in the direction of the longitudinal axis of said rod, and separate means varyingthe and wherein in addition there is provided aovacuum tube having ,a plurality of electrodes,.said coil having its ends operatively connected to two -4' electrodes of said vacuum tube; o 10. The combination as claimed in claim 18 wherein the means for varying'the field flowingthrough said rod comprises a coil about said rod I and wherein there is provided in additionan electron discharge device having an anode, a

cathode and a grid, the ends of said field varying coil being operatively connected to the grid atively connected to two electrodes of said device.

12. The combination as claimed in claim 8 wherein said field varying means comprises a coil about said rod, and wherein in addition there is provided a vacuum tube havingan anode, a cathode and a grid; and, a resonant circuit, said resonant circuit'being connected between said grid, and cathode of said tube, and said coil being connected across said resonant circuit.

CLARENCE w. HANSELL. 

